1 Cells And The Immune System Flashcards

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1
Q

How is each type of cell specific?

A

Each type of cell has specific molecules on its surface that identify it. These molecules include proteins and enable the immune system to identify: pathogens, cells from other organisms of the same species, abnormal body cells, and toxins.

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2
Q

Define antigen.

A

Molecule, usually proteins, that can generate an immune response when detected by the body. Usually found on surface of cells.

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3
Q

Describe the effect of antigen variability on disease and disease prevention.

A
  • antigens on surface of pathogen activate primary response.
  • when infected 2nd time with same pathogen which has same antigens, they activate secondary response
  • some pathogens can change their surface antigens, this antigen variability is called antigenic variation.
  • means when infected 2nd time, memory cells produced from first infection will not recognise different antigens so immune system has to carry out primary response.
  • primary response takes time to get rid of infection
  • antigenic variation also makes it difficult to develop vaccines against some pathogens.
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4
Q

Describe phagocytosis of pathogens

A
  • phagocyte recognises foreign antigens on pathogen.
  • cytoplasm of phagocyte engulfs pathogen
  • pathogen now contained in phagocytic vacuole in cytoplasm of phagocyte
  • lysosome fuses with phagocytic vacuole. Lysozymes break down pathogen.
  • phagocyte then presents pathogens antigens to activate other immune system cells.
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5
Q

Describe the difference between active and passive immunity.

A
  • active requires exposure to antigen whereas passive doesn’t
  • active takes a while for production to develop whereas passive is immediate
  • active, memory cells produced whereas passive they aren’t
  • active protection is long-term because antibody is produced in response to complimentary antigen being present in body. Whereas passive protection is short-term because antibodies given are broken down.
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6
Q

How does the use of vaccines provide protection for individuals.

A
  • vaccines contain antigens, may be free or attached to a dead or attenuated pathogen, that cause body to produce memory cells against particular pathogen, without pathogen causing disease.
  • vaccines protect individuals, because they reduce occurrence of disease, those not vaccinated also less likely to get disease because fewer people to catch it from. This called herd immunity.
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7
Q

Describe the structure of HIV.

A
  • core contains genetic material (RNA) and some proteins.
  • outer coating of protein called capsid.
  • extra outer layer called envelope, made of membrane stolen from cell membrane of a previous host cell.
  • loads of copies of an attachment protein sticking out from envelope that help HIV attach to host helper T-cell
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8
Q

Explain how HIV replicates inside its host’s helper T-cells.

A
  • attachment protein attaches to receptor molecule on cell membrane of host helper T-cell.
  • capsid released into cell, where it uncials and releases genetic material into cells cytoplasm
  • inside cell, reverse transcriptase is used to make complementary strand of DNA from viral RNA template.
  • from this, double stranded DNA is made and inserted into human DNA.
  • host cell enzymes used to make viral proteins from viral DNA found within human DNA.
  • viral proteins assembled into new viruses, which bud from cell and go on to infect others.
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9
Q

Explain how HIV causes symptoms of AIDS

A
  • HIV infects helper T-cells, which act as host cells for virus. Without enough helper T-cells immune system is unable mount an effective response to infections because other immune system cells don’t behave how they should.
  • people infected with HIV develop AIDS when helper T-cell numbers in body reach critically low level.
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10
Q

Explain why antibiotics are ineffective against viruses.

A
  • antibiotics kill bacteria by interfering with their metabolic reactions. Target bacterial enzymes and ribosomes used in those reactions.
  • bacterial enzymes and ribosomes different to human ones. Antibiotics designed to only target bacterial ones so don’t damage human cells.
  • viruses don’t have own enzymes and ribosomes, so because human viruses use human enzymes and ribosomes to replicate, antibiotics can’t inhibit them.
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11
Q

Describe the ethical issues associated with the use of vaccines and monoclonal antibodies.

A
  • vaccines tested on animals before humans
  • testing vaccines on humans can be tricky. Eg. Volunteers may put themselves at unnecessary risk of contracting disease because they think they’re fully protected.
  • some people don’t want to take vaccine due t risk of side effects, but still protected because of herd immunity- other people think unfair.
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12
Q

Describe the ELISA (Enzyme-linked immunosorbent assay) test.

A
  • tests allows you to see if patient has any antibodies to a certain antigen or any antigen to a certain antibody.
  • used to test for:pathogenic infections, allergies.
  • in test an antibody with an enzyme attached to it is used. This enzyme can react with substrate to produce coloured product. This causes solution in reaction vessel to change colour.
  • colour change demonstrates that antigen or antibody of interest is present in sample.
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13
Q

What are the 2 types of ELISA test.

A
  • direct ELISA, uses single antibody that’s complimentary to antigen testing for.
  • indirect ELISA , uses 2 different antibodies.
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14
Q

Describe the use of monoclonal antibodies in targeting drugs to specific cell types.

A
  • monoclonal antibodies can be made to bind to any target cell
  • attach drugs to antibodies, which then bind to target cell
  • drug and antibody will only bind to target cells, so side effects of antibody-based drug are lower than other drugs as accumulate near specific cells.
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15
Q

Describe the use of monoclonal antibodies in medical diagnosis.

A
  • monoclonal antibodies fixed to a plate
  • sample added, if antigen present it forms antigen-antibody complex
  • rinsed to remove unbound antigens
  • some monoclonal antibody added with enzyme/colour attached
  • rinsed to remove unbound antibodies
  • observe to look for marker , if enzyme add substrate there’s colour change.
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16
Q

Describe the response of T lymphocytes to a foreign antigen.

A
  • T-cell has receptor proteins on its surface which bind to complementary antigens presented to it by phagocytes. This activates T-cell.
  • helper T-cells release chemical signals that activate and stimulate phagocytes a cytotoxic T-cells which kill abnormal and foreign cells. Helper T-cells also activate B-cells.
17
Q

Describe the response of B lymphocytes to a foreign antigen.

A
  • B-cells covered with antibodies
  • each B-cell has different shaped antibody on its membrane, so different ones bind to different shaped antigens.
  • when antibody on surface of B-cell meets complimentary antigen, it binds to it. Forming an antigen-antibody complex.
  • this, together with substances released from helper T-cells, activates the B-cell.this process called colonial selection.
  • activated B-cell divides into plasma cells.
18
Q

Define antibody

A

Proteins made up of chains of amino acids

19
Q

How is an antigen-antibody complex formed?

A

Plasma cells secrete antibodies specific to antigen (monoclonal antibodies) they bind to antigens on surface of pathogen to form lots of antigen-antibody complexes. Antibody has 2 binding sites so can bind to two pathogens at same time. Means that pathogens clump together- called agglutination. Phagocytes bind to the antibodies and phagocytose many pathogens at once. Process leads to destruction of pathogens carrying this antigen in the body.

20
Q

Explain primary response.

A
  • antigen enters body for first time it activates immune system. This called primary response. (PR)
  • PR slow because aren’t many B-cells that can make antibody needed to bind to it
  • eventually body will produce enough of right antibody to overcome infection. Meanwhile infected person shows symptoms of disease
  • after being exposed to antigen, both T-cells and B-cells produce memory cells, these will remain in body for long time.
  • this person now immune, their immune system has ability to respond quickly to a second infection.
21
Q

What do memory T-cells remember?

A

The specific antigen and will recognise it the second time it’s infected with that pathogen.

22
Q

What do memory B-cells record?

A

The specific antibodies needed to bind to the antigen.

23
Q

Explain secondary response.

A
  • if same pathogen enters body again, immune system will produce a quicker, stronger, immune response
  • clonal selection happens faster. Memory B-cells are activated and divide into plasma cells that produce the right antibody to the antigen. Memory T-cells are activated and divide into the correct type of T-cells to kill the cell carrying antigen
  • often gets rid of pathogens before you begin to show symptoms.
24
Q

What is aids?

A

condition where immune system deteriorates and eventually fails. Someone with AIDS more vulnerable to other infections.